Avoid splitting things up
That language is a real, dynamic and complex phenomenon, no one can deny. The problem is when people attempt to split this complex phenomenon into parts that are supposedly coherently split but are of little help to those who try to make sense out of them. This is the way languages are thought at elementary and high schools in several parts of the world, and the result is that only few people in few countries manage to learn languages merely through attending regular classes at school. In Brazil, for example, no one is expected to learn either English or Spanish by attending classes at a normal school. Those who are seriously committed to learning a language have to pay for classes at private language schools and even there they may be subject to the same wrong methods that are used in ordinary schools and end up learning very little and being far from conversational after 5 to 6 years. Whether those schools teach the wrong way on purpose, in order to retain the student as long as possible, or just due to absolute lack of competence, is beyond the scope of this article. The most important thing to do is to realize what is being done wrong and how to fix it up as soon as possible.
The way languages are taught in many places around the world is a relic of the way Latin was taught. Latin is a language with a complex grammar, especially morphology: several cases and declension patterns, several personal endings for the verbs, several verb tenses. Since Latin had long been a dead language, the books and classes tended to focus on understanding its grammar and learning its form by rote, so that students would be able to translate classical Latin texts. The vocabulary covered was the one to be found in poetry and essays from classical authors. Little or no emphasis was put on words that would help students describe the world around them. Conversation was out of question: after all, Latin was not spoken anymore.
As a result, people would learn grammar patterns in terms of complexity, regardless of usage frequency. And since each of these patterns was complex on its own and demanded several forms to be memorized, they would take months or a whole semester to be fully memorized before moving on to the next topic. In the first semester, for example, a student would learn the present tense. They would have no contact with texts that talked about the past or the future. They would memorize the present fully and only then proceed to the past, the imperative, the future. So, an ordinary student would need 1 to 2 years to be able to mention something that happened the past day or make a simple request.
If this method proves to be efficient for Latin, leave alone modern languages. Why would a student have to wait three semesters in order to be able to say something about the future in Spanish, for which most of the time they only need to know a few patterns? A student who learns the forms yo canto, tú cantas, él canta for the present does not need 3 semesters to recover from this "intense memorization" in order to learn the past tense forms yo canté, tú cantaste, él cantó And the future yo cantaré, tú cantarás, él cantará. Yet this is what happens in several language schools where people are getting so little for their money. This is not what they need: they need to know basic and less basic sentences that involve grammar topics reputed as more complex but by no means are of lesser frequency. The subjunctive, for example, is considered a nightmare for students of Romance languages. So, it is relegated for further levels at a course, as an advanced topic. Do people really think it would take months or years for someone who moved into a Spanish-speaking country to come across a sentence in the subjunctive? As a speaker of Portuguese with some knowledge on Spanish, I am pretty much certain it would take no more than a few hours.
The message is clear: the fact that a subject is reputed as complex does not mean it should be elided from a student's life until they are supposedly prepared for dealing with it. Real life will demand them to at least recognize it as soon as possible. So, people who write language books for classroom usage should be aware of that and stop postponing the presentation of important topics artificially. Instead, they should present an overview of them and introduce them little by little in context, so that students would get in touch with a real form of the language, not an artificially devised one where there is no past or no future (or no subjunctive, for that matter) throughout most of their lives as students.